Ms. Warren could have been among them but for strong disapproval from Republicans. She was the leading candidate to run the new Consumer Financial Protection Bureau in 2011, but as opposition grew, President Barack Obama turned instead to former Ohio Attorney General Richard Cordray.

Ms. Warren, a Harvard Law professor who helped set up the CFPB, first gained national attention as chairman of the Congressional Oversight Panel overseeing the 2008 bank bailouts.

On Thursday, instead of seeking an update on rules being developed for Wall Street, Ms. Warren asked the regulators when was the last time they took a financial firm to trial.

“I’m really concerned that ‘too big to fail’ has become ‘too big for trial,’” Ms. Warren told the regulators at the witness table, including the chairman of the Securities and Exchange Commission and the Comptroller of the Currency. “That just seems wrong to me.”

Her rebuke brought applause from supporters in the audience.

Long a critic of the way big banks treat consumers, Ms. Warren’s aggressive questioning could signal that she will scrutinize Washington officials and bankers alike. An aide to Ms. Warren declined to comment.

She echoed criticism of the longstanding practice of allowing firms to settle SEC complaints without a formal admission or denial of guilt. Companies typically seek settlements with the SEC to head off major damage to their stock price or brand from a drawn-out court battle.

As for going to trial, Comptroller Thomas Curry said his agency has “not had to do it as a practical matter to achieve our supervisory goals.” SEC Chairman Elisse Walter said her agency looks “at the distinction between what we could get if we go to trial and what we could get if we don’t.”

About Washington Wire

Washington Wire is one of the oldest standing features in American journalism. Since the Wire launched on Sept. 20, 1940, the Journal has offered readers an informal look at the capital. Now online, the Wire provides a succession of glimpses at what’s happening behind hot stories and warnings of what to watch for in the days ahead. The Wire is led by Reid J. Epstein, with contributions from the rest of the bureau. Washington Wire now also includes Think Tank, our home for outside analysis from policy and political thinkers.